The present invention relates to a method for identifying one or more simultaneously occurring partial discharge sources from partial discharge measurement signals of an electrical device to which an AC voltage is applied.
Partial discharges occur in electrical devices to which an AC voltage is applied if there are weak spots in the electrical insulation. A prominent example thereof are partial discharges that occur in particular in high-voltage power lines or the porcelain insulators affixing them to the towers when it is raining or the weather is damp, and are usually perceived as a crackling sound. In the open air, such partial discharges are non-critical. However, if they occur in encapsulated devices, they might cause a sparkover and destroy the device, especially if, for space saving reasons, the lines and devices are installed in gas-insulated switching systems filled with pressurized insulating gas.
In a gas-insulated system, a partial discharge may be caused by factors such as contaminations in the gas-insulated system, internal defects such as scratches or burrs on the inside of the housing or the inner conductor, or inaccurate assembly. Such partial discharges have a great impact on the operating performance of the gas-insulated system and might cause disastrous accidents if they are not identified early on.
The monitoring and evaluation of such gas-insulated systems is therefore an important instrument for preventive maintenance and the avoidance of disruptive incidents.
External and internal sensors for detecting partial discharges are, for example, known from DE 10 2009 034 062 A1. Such sensors detect partial discharge signals occurring in a gas-insulated system. Although partial discharges can be measured with such sensors, it has thus far not, or not in a satisfactory manner, been possible to allocate the measured partial discharges to the actual partial discharge sources. To date, it has not been possible to identify a plurality of simultaneously occurring partial discharge sources.
As a consequence, there is a need for a reliable and unambiguous identification of partial discharge sources from measured partial discharge measurement signals, in particular when a plurality of partial discharge sources in electrical devices to which an AC voltage is applied occur simultaneously.